Dynamag®
"Force under control"
The DYNAMAG® is a magnetoelasticdynamometer designed forthe non-contact mechanical tension measurement in the steel constructions like cable-stayed, suspended or extradosed bridges, ground anchors, pile walls, embankments, beams and plates. It can be used for the quality checks of the prestressing process or for the long term monitoring of the state of the observed construction. The industrial design of the measurement system is registered in the European Union and the utility model of the measurement system is registered in the Czech Republic.
How does it work?
There is nothing magic about the “MAG” in the name of this measurement system. This only describes the physical principles of the measurement method which is based on the magnetoelastic phenomenon. It measures the changes of the magnetoelastic characteristics of ferromagnetic materials during their mechanical load. The relative permeability µr depends on the tension force.
The DSCS magnetoelastic sensor is the basic element of the measurement system.It is shaped as a hollow cylinder which is installed by sliding onto a measured element. It consists of plastic body, electrical winding and stainless cover. It is connected by the cable to the read-out unit. The portable read-out unit is suitable for the one-time measurements, stationary system can be integrated into a complex monitoring system. This system involves the read-out unit and a series of multiplexers which allow the connection of 4-64 sensors. The measured data are saved in a measurement file which can be immediately interpreted in a graphic form of sent via internet on a particular server.
Where does it work?
The DYNAMAG® measurement system has been applied on many constructions in the Czech Republic, Slovakia and abroad. The most significant applications have been tension measurement of the permanent and temporary ground anchors in Blanka tunnel, Prague, continuous monitoring of the ground anchors on the Turecký vrch railway tunnel, Nové Mesto nad Váhom, tension measurement in the ground anchors in the retaining wall around R1, Nitra, tension measurement in the construction of flood control dam in the Mělník port, tension measurement in the rods of the suspended bridge in the industrial zone, Třinec-Baliny or monitoring of the tension in the additional prestressed reinforcement of the bridge in Chotěbuz during a static load test. It was also used for the continous monitoring of the tension in the hangers of the retractable roof of BC Place Stadium, Vancouver, Canada,where it provided an automatic control of the snow load.
The DYNAMAG® measurement system can be generally used for ferromagnetic materials. Most of the materials that are commonly used in building industry fulfil this condition. This can also be proved in our laboratory. Considering the shape of the sensor the ideal use is for the cylindrically shaped measured elements (strand, cable or rod). The sensor is standardly installed before the prestressing process starts. If necessary, a special winding equipment can be used in order to install the sensor onto an existing construction.
Why to use it?
The main advantage of the DYNAMAG® measurement system lies especially in the high resistance of the sensors and a possible long-term usage under harsh field conditions. They are resistant to shocks, vibrations, water, salt water, water under pressure, chemicals and radioactivity.
They represent a non-contact and non-destructive method therefore the intervention into the measured construction is not necessary. The measurement can be realised without a direct physical contact (e.g. through an anti-corrosive protection).
The sensors can be sealed in concrete or completely covered during the construction process.
Use of the Dynamag® system
The stadium and the building
The stadium and the building
The DYNAMAG® measurement system can be used for the mechanical tension measurement in cable-stayed and prestressed steel constructions like roofs of the sport stadiums, halls and large buildings. The 72 sensors that are installed on the retractable roof in Vancouver, Canada provide continual monitoring of the snow load and control automatic compensation of the pressure by air cushions.
The bridge and the pole
The DYNAMAG® measurement system can be used for the mechanical tension measurement in cable-stayed, suspended and extradosed constructions like bridges and poles. It is possible to measure the tension during the tensioning process and thus check its quality, during the static load of the construction or in the periodic term inspections. The data from the continual monitoring can be transmitted by the GSM technology into a particular information system. The tension measurement in the rods of the suspended bridge in the industrial zone, Třinec-Baliny was done by the split sensors that had been installed subsequently while a special winding equipment was used as well. For the bridge in Chotěbuz, the sensors for the additional prestressed reinforcement of the bridgewere installed during the static load test.
The ground anchor and the vault
The DYNAMAG® measurement system can be used for the mechanical tension measurement in prestressed steel-concrete constructions like ground anchors and mine anchors, which serve as a protection for retaining walls, bridge piles, flood control dams or tunnels. It is possible to measure the tension during the tensioning process and check its quality, during the static load of the construction or in the periodic term inspections. The data from the continual monitoring can be transmitted by the GSM technology into a particular information system. The DYNAMAG sensors have been used for the measurement of the permanent and temporary ground anchors in tunnel Blanka, Prague, for continous monitoring of the ground anchors on the Turecký vrch railway tunnel, Nové Mesto nad Váhom, for tension measurement in the ground anchors in the retaining wall around R1, Nitra, tension measurement in the construction of the flood control dam in the Mělník port.
Frequently Asked Questions
1 / How accurate is the measurement?
The measurement system measures the magnetic flux as a primary value with the resolution of 1 µWb that makes it possible to obtainthe extended combined uncertainty of the measurement up to 1% of the applied mechanical tension. The uncertainty of the measurement is influenced by magnetoelastic characteristics of the measured material, filling sensor coefficient, magnetic environment of the sensors, movement of the measured element in the sensor and temperature. In case of the calibration of the sensor in situ, the measurement is tied to the calibrated tensioning equipment. This calibration simultaneously eliminates the influence of the characters of the material and of the magnetic environment. The influence of the filling of the sensor is eliminated by the usage of an optimal dimension of the sensor regarding the diameter of the measured element. Both the axial and the radial shift of the material in the sensor are usually eliminated during the installation of the sensor by a fixing element or by inducing of an initial tension at the beginning of tensioning process. The temperature dependence is automatically corrected by the measuring software. In case of the laboratory calibration, the uncertainty of the measurement increases up to 5%. The uncertainty of the measurement by the split sensors which are additionally winded onto the measured construction is about 10%.
2 / What is the range of the measurement?
The measurement system measures the magnetic flux as the primary value in the range of 1 mWb which makes it possible to cover the range of the applied mechanical tension from 0 kN up to the limit of elasticity of the material. The optimal setting for concrete configuration is provided by a special configuration file assigned to the sensor. It is impossible to overload the sensor or to damage it by shock pulses.
3 / Is it possible to measure the already existing constructions?
The measurement system is applicable also to the measurement of the tension in the existing steel or prefabricated constructions. This application requires the installation of the split sensor while using a special winding equipment. The accuracy of the measurement is significantly lower than with the normal sensors.
The demand form
